ThemeManager

Please Note: All code surrounded by [ ] needs to be replaced with the correct value by you.

What is the ThemeManager

The ThemeManager provides several options to provide themes for your application or control library. For example MahApps.Metro and Fluent.Ribbon use it to provide different themes to the user.

In the following sections the usage will be described by the sample usage at MahApps.Metro.

Create built in themes

Using XamlColorSchemeGenerator

You can provide built in themes in your application or library by running the XamlColorSchemeGenerator while building or via command line. For detailed information about the usage, please visit the XamlColorSchemeGenerator site.

Using ResourceDictionaries

Please note: It is not recommended to use this approach as you might miss the addition of new required resources when new versions of libraries are released.

You may also provide a custom ResourceDictionary with all the needed resources.

Get yourself a copy of the required Template
- MahApps.Metro: https://github.com/MahApps/MahApps.Metro/blob/main/src/MahApps.Metro/Styles/Themes/Theme.Template.xaml
- Fluent.Ribbon: https://github.com/fluentribbon/Fluent.Ribbon/blob/master/Fluent.Ribbon/Themes/Themes/Theme.Template.xaml
Replace all items surrounded by double curly braces {{ Content to Replace }}
Remember to create all needed variants. E.g.: If you want to support light and dark themes you will need to implement both.

Changing the theme at runtime

Change the theme using a built in theme

First of all you need to add the following namespace in your using section:

using ControlzEx.Theming;

now you can apply the Theme of your choice to your App, to a specific Window or any FrameworkElement. Just call this line in your code:

ThemeManager.Current.ChangeTheme([Affected item], "[Name of the theme]");

Where [Affected item] may be:

Application.Current
this
any Window
any Control
any FrameworkElement

and [Name of the theme] is any valid theme name, e.g. Dark.Blue in MahApps.Metro.

The ThemeManager can be called from different locations, for example:

Inside the constructor of your App.xaml.cs
Inside the constructor of your Window
In a Click-Event of a Button
In your ViewModel

Example

If you want, for example, set your application theme to Dark.Red, when the user clicks a button called "ButtonChangeTheme" you can do this:

private void ButtonChangeTheme_Click(object sender, RoutedEventArgs e)
{
    ThemeManager.Current.ChangeTheme(App.Current, "Dark.Red");
}

Sync your theme with the Windows theme

It is also possible to sync your Theme with the users Windows theme. The first step is again to add the following namespace in your using section:

using ControlzEx.Theming;

Now you need to define if you want to sync the BaseColor, the Accent or both:

ThemeManager.Current.ThemeSyncMode = ThemeSyncMode.[DoNotSync|SyncAll|SyncWithAccent|SyncWithAppMode|SyncWithHighContrast];

The table below explains the available ThemeSyncModes:

ThemeSyncMode	Description
DoNotSync	No sync at all
SyncAll	Gets or sets whether changes to the "app mode", accent color and high contrast setting from windows should be detected at runtime and the current Theme be changed accordingly.
SyncWithAppMode	Gets or sets whether changes to the "app mode" setting from windows should be detected at runtime and the current Theme be changed accordingly.
SyncWithAccent	Gets or sets whether changes to the accent color settings from windows should be detected at runtime and the current Theme be changed accordingly.
SyncWithHighContrast	Gets or sets whether changes to the high contrast setting from windows should be detected at runtime and the current Theme be changed accordingly.

Explanation: "app mode" is the windows terminology for base color like "dark" or "light".

Please note: Once you enable theme sync you should not change the theme manually as manual changes would be overwritten as soon as some event occurs that triggers a theme sync. Such events could be triggered by various things like changes to display settings, connecting/disconnecting via RDP etc..

To actually sync the Theme call this line:

ThemeManager.Current.SyncTheme();

Note: If you want to sync just a part of the Theme and use a custom Theme make sure that the Theme is correctly added to the ThemeManager.

Change the theme by creating a custom one

First of all you need to add the following namespace in your using section:

using ControlzEx.Theming;

Optional: If you wish to use HSL to create the AccentColors instead of semi-transparent colors, you can set this in the options:
```
RuntimeThemeGenerator.Current.Options.UseHSL = [true/false];
```

Now you can create a new Theme by providing the Color you wish:

Theme newTheme = new Theme("[Name of the generated theme]",
                           "[DisplayName of the generated theme]",
                           [ThemeManager.BaseColorLight or ThemeManager.BaseColorDark],
                           "[AccentName]",
                           [AccentColor],
                           new SolidColorBrush(AccentColor),
                           true,
                           [IsHighContast: false/true]);

Adjust all parameters surrounded by [] in the above snipped to your needs.

Optional: Add or override any Resources in the new Theme if needed, e.g.:

newTheme.Resources["MahApps.Colors.Highlight"] = HighlightColor;
newTheme.Resources["MahApps.Brushes.Highlight"] = new SolidColorBrush(HighlightColor);

Optional: Add the Theme to the current ThemeMangers collection:
```
ThemeManager.Current.AddTheme(newTheme);
```
Apply new Theme
```
ThemeManager.Current.ChangeTheme([Affected item], newTheme);
```
Where [Affected item] may be:
- Application.Current
- this
- any Window
- any Control
- any FrameworkElement

Override the LibraryThemeProvider

If you want to have even more control about the theme generation you can override the LibraryThemeProvider with your own provider. In the following sample we will show how to do this for MahApps.Metro.

Create a new class which derives from a LibaryThemeProvider, in our case MahAppsLibraryThemeProvider
```
public class MyLibraryThemeProvider : MahAppsLibraryThemeProvider
```

Override the static DefaultInstance

public static new readonly MyLibraryThemeProvider DefaultInstance = new MyLibraryThemeProvider();

Override the Methods you like (most likely you want to override this):

public override void FillColorSchemeValues(Dictionary<string, string> values, RuntimeThemeColorValues colorValues)
{
    // Check if all needed parameters are not null
    if (values is null) throw new ArgumentNullException(nameof(values));
    if (colorValues is null) throw new ArgumentNullException(nameof(colorValues));

    // Add the values you like to override
    values.Add("MahApps.Colors.AccentBase", "[AccentBaseColor]");
    values.Add("MahApps.Colors.Accent",     "[AccentColor]");
    values.Add("MahApps.Colors.Accent2",    "[AccentColor2]");
    values.Add("MahApps.Colors.Accent3",    "[AccentColor3]");
    values.Add("MahApps.Colors.Accent4",    "[AccentColor4]");

    values.Add("MahApps.Colors.Highlight",  "[HighlightColor]");
    values.Add("MahApps.Colors.IdealForeground", colorValues.IdealForegroundColor.ToString(CultureInfo.InvariantCulture));
}

Register your provider to your App or in Generic.xaml of your controls library

a. add the following namespace:

xmlns:theming="clr-namespace:BIA_Controls.Theming"

b. add this line in the Resources section:

<theming:MyLibraryThemeProvider x:Key="{x:Static theming:MyLibraryThemeProvider.DefaultInstance}" />

Hints for resource lookup: The default implementation will look for resources that contain /themes/ in their resource path. If you want to change that behavior you can override IsPotentialThemeResourceDictionary or if you want to completely change how library themes are resolved for your provider you can override GetLibraryTheme.

Below is a complete sample with some customization:

If the user selects the Light theme, the accent colors have the same appearance as the transparent ones, but they are solid.
If the user selects the Dark theme, the accent colors are a bit brighter than in the original implementation.
The HighlightColor is calculated differently
The gray shades are calculated to be equally distributed from black to white

public class MyLibraryThemeProvider : MahAppsLibraryThemeProvider
{
    /// <inheritdoc/>
    public static new readonly MyLibraryThemeProvider DefaultInstance = new MyLibraryThemeProvider();

    public override void FillColorSchemeValues(Dictionary<string, string> values, RuntimeThemeColorValues colorValues)
    {
        // Check if all needed parameters are not null
        if (values is null) throw new ArgumentNullException(nameof(values));
        if (colorValues is null) throw new ArgumentNullException(nameof(colorValues));

        bool isDarkMode = colorValues.Options.BaseColorScheme.Name == ThemeManager.BaseColorDark;
        Color baseColor = (Color)ColorConverter.ConvertFromString(colorValues.Options.BaseColorScheme.Values["MahApps.Colors.ThemeBackground"]);
        Color accent = colorValues.AccentBaseColor;
        double factor = isDarkMode ? 0.1 : 0.2;

        // Add the values you like to override
        values.Add("MahApps.Colors.AccentBase", accent.ToString(CultureInfo.InvariantCulture));
        values.Add("MahApps.Colors.Accent", AddColor(accent, baseColor, factor * 1).ToString(CultureInfo.InvariantCulture));
        values.Add("MahApps.Colors.Accent2", AddColor(accent, baseColor, factor * 2).ToString(CultureInfo.InvariantCulture));
        values.Add("MahApps.Colors.Accent3", AddColor(accent, baseColor, factor * 3).ToString(CultureInfo.InvariantCulture));
        values.Add("MahApps.Colors.Accent4", AddColor(accent, baseColor, factor * 4).ToString(CultureInfo.InvariantCulture));

        values.Add("MahApps.Colors.Highlight", AddColor(accent, isDarkMode ? Colors.White : Colors.Black, 0.8).ToString(CultureInfo.InvariantCulture));
        values.Add("MahApps.Colors.IdealForeground", colorValues.IdealForegroundColor.ToString(CultureInfo.InvariantCulture));

        // Gray Colors
        for (int i = 1; i <= 10; i++)
        {
            values.Add($"MahApps.Colors.Gray{i}", GetShadedGray(i / 11d, isDarkMode).ToString(CultureInfo.InvariantCulture));
        }
    }

    private static Color GetShadedGray(double percentage, bool inverse = false)
    {
        if (inverse)
        {
            percentage = 1 - percentage;
        }

        return Color.FromRgb((byte)(percentage * 255), (byte)(percentage * 255), (byte)(percentage * 255));
    }

    private static Color AddColor(Color baseColor, Color colorToAdd, double? factor)
    {
        byte firstColorAlpha = baseColor.A;
        byte secondColorAlpha = factor.HasValue ? (byte)(factor * 255) : colorToAdd.A;

        byte alpha = CompositeAlpha(firstColorAlpha, secondColorAlpha);

        byte r = CompositeColorComponent(baseColor.R, firstColorAlpha, colorToAdd.R, secondColorAlpha, alpha);
        byte g = CompositeColorComponent(baseColor.G, firstColorAlpha, colorToAdd.G, secondColorAlpha, alpha);
        byte b = CompositeColorComponent(baseColor.B, firstColorAlpha, colorToAdd.B, secondColorAlpha, alpha);

        return Color.FromArgb(255, r, g, b);
    }

    /// <summary>
    /// For a single R/G/B component. a = precomputed CompositeAlpha(a1, a2)
    /// </summary>
    private static byte CompositeColorComponent(byte c1, byte a1, byte c2, byte a2, byte a)
    {
        // Handle the singular case of both layers fully transparent.
        if (a == 0)
        {
            return 0;
        }

        return System.Convert.ToByte((((255 * c2 * a2) + (c1 * a1 * (255 - a2))) / a) / 255);
    }

    private static byte CompositeAlpha(byte a1, byte a2)
    {
        return System.Convert.ToByte(255 - ((255 - a2) * (255 - a1)) / 255);
    }
}

Detect the current theme

You can get the current applied theme of the entire App, a single Window or any FrameworkElement. To do so import this namespace to your usings:

using ControlzEx.Theming;

Now you can call this statement to get the current theme:

Theme currentTheme = ThemeManager.Current.DetectTheme([ThemedItem]);

where ThemedItem may be:

Application.Current
this
any Window
any Control
any FrameworkElement

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